1. Field of the Invention
This invention relates to a rotation shaft seal, especially, a rotation shaft seal used to seal high-pressure fluid such as CO2 gas.
2. Description of the Related Art
Recently, pressure of sealed fluid (such as CO2) has been increasing in use of compressors for automobiles. So the applicant of the present invention proposed a rotation shaft seal as shown in FIG. 9 (refer to Japanese provisional publication No. 2004-353765). In FIG. 9, a rubber sealing portion 33 having a sliding portion S0 which contacts surface of a rotation shaft 32 and an outer case 34 are unified, an inner brim portion 36 on a high-pressure side C of the outer case 34 is covered by the rubber sealing portion 33, and, disposing the sliding portion S0 of the sealing portion 33 on an axis-orthogonal face P0 including the inner brim portion 36, a lip portion 37 of the sealing portion 33 slides on the rotation shaft 32 with low contact pressure when receiving high pressure from the high-pressure side C.
In a rotation shaft seal precedent to the conventional example in FIG. 9, excessive contact pressure is generated on the surface of the rotation shaft in rotation and early abnormal abrasion is generated on the sliding portion of the rubber lip along with the excessive contact pressure because the configuration of the rubber lip is having an L-shaped cross-section, largely extended to the sealed fluid side, and a large area of pressure-receiving portion (refer to Japanese provisional publication No. 2003-97723).
As described above, in the conventional example shown in FIG. 9, the early abnormal abrasion of the lip portion 37 on the sliding portion S0 can be effectively prevented. However, it has been revealed that a problem of fluid (gas) leakage within a long period of time from the high-pressure side C to the low pressure side E, namely, inner-leak problem is not solved by the conventional construction in FIG. 9.
Concretely, although a seal element 38 of resin such as PTFE is disposed on the low-pressure side E and two inner cases 39 and 40 are holding an axis-orthogonal portion 38a of the seal element 38 as to be sandwiched, an experiment conducted by the inventors of the present invention revealed generation of inner leak as shown with arrows F1 and F2, broken lines, and an arrow F3 in FIG. 8 (described later).
Recently, it has been desired to make the pressure of the sealed fluid (gas) higher, and it has been revealed that the inner leak of the fluid such as gas tending to have high pressure can not be prevented with the conventional example shown in FIG. 9 in which the faces 41 and 42 of the axis-orthogonal portion 38a of the seal element 38 are simply held by the inner cases 39 and 40.
It is therefore an object of the present invention to provide a rotation shaft seal which solves all of the above-described problems, prevents inner leak, and performs stable and excel lent sealability for sealing high-pressure gas.